#include<bits/stdc++.h>

using namespace std;

struct bagNode
{
	double m,v;
	double average;
};

bagNode a[100];

int cmp(const void* a,const void* b)
{
	return -(((bagNode*)a)->average -((bagNode*)b)->average);
}
int main()
{
	double n,t;
	cin>>n>>t;
	for(int i = 0 ; i < n ;i++)
	{
		cin>>a[i].m>>a[i].v;
		a[i].average = a[i].v/a[i].m;
	}
	qsort(a,n,sizeof(bagNode),cmp);
	double sum = 0;
	for(int i = 0 ; i <n ; i++)
	{
		if(t >= a[i].m)
		{
			sum = sum + a[i].v;
			t = t - a[i].m;
		}
		else{
			sum = sum + t * 1.0 * a[i].average;
			break;
		}
	}
	printf("%.2f",sum);
}
